<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    div {
      width: 200px;
      height: 200px;
      background-color: green;
    }
  </style>
</head>

<body>

  <div class="box"></div>
  <script>
  let n =   setInterval(function () {
      console.log('123');
    }, 1000)
    console.log(n);
    clearInterval(n)
    const box = document.querySelector('.box')
    box.style.width = '100px'
    box.style.height = '100px'
    box.style.backgroundColor = 'pink' 
  </script>
</body>

</html>